What would the children’s book world look like if “Harry Potter”had never popped into J.K. Rowling’s head, as she’s described it, fully formed? Hypotheticals are never easy, but a “Harry Potter”-less world ― well, that’s just about impossible to conceive.

By the same token, untangling Rowling’s influence from the greater arc of children’s literature over the past two decades is a fraught task. Her “Potter” saga inspired frenzied release parties, staggering numbers of pre-orders, millions of words of fan fiction and, as it stands now, nine feature films: It’s an easy assumption that this seminal series fundamentally changed middle-grade and YA fiction.

And it surely did. The market for these kinds of books, especially fantasy, exploded during the early aughts, as ”Harry Potter” took off. Not just lightweight series like “The Baby-Sitters Club” or one-offs like The Fault in Our Stars, either; publishers began offering kids blockbuster series like “The Hunger Games,” “Twilight,” and “Divergent.” Then again, plenty of authors were already offering well-crafted fantasy and realism for young readers. What can really be laid to Rowling’s account?

Twenty years after Harry first ventured into the world with the initial publication of Harry Potter and the Philosopher’s Stone, we’re still wondering what the phenomenon has really meant for kids books and the publishing world at large, and where we would be without it. “Harry Potter” sparked a furor that seemed totally unprecedented in the world of children’s literature. The books themselves, though ― not much about them was totally unprecedented.

Aside from the whole magic aspect, tales of Hogwarts fall squarely into the beloved tradition of books about kids away at school. “Obviously it was building not on just fantasy but the boarding school books,” Peter Glassman, founder of the children’s bookshop Books of Wonder, told news. Tom Brown’s School Days, The Little Princess, Daddy-Long-Legs, Malory Towers and other boarding school books free up their youthful protagonists for adventure by separating them from parents and family obligations, placing them in a setting where their relationships with other children, and their round-the-clock hijinks, can take center stage.

The boarding school has proven to be a perfect setting for a fantasy novel throughout the past century. “The magical wizarding school had been done before,” pointed out Joe Monti, the editorial director of Saga Press and a longtime player in the children’s literature arena, in an email to news. He specifically praised Ursula K. Le Guin’s classic series “Earthsea” and Diana Wynne Jones’s “Chrestomanci” heptalogy, but it was a far more pervasive trope than we may realize in a post-“Potter” world. (Now, when you Google “wizarding school,” the featured snippet and nine of the 10 first-page results are specifically about Rowling’s fictional schools, which include Hogwarts and other non-British schools she has named, such as Beauxbatons and Ilvermorny. The 10th is the Wikipedia page for fictional wizarding schools, which prominently features the “Harry Potter” universe.)

Before Hogwarts, there were a number of wizarding schools that featured elements of Rowling’s hit. In Jane Yolen’s 1991 Wizard’s Hall, an 11-year-old boy named Henry finds himself learning spells in a magical school where paintings speak. Jill Murphy’s ”Worst Witch” series, originally begun in the 1970s, featured the inept Mildred Hubble, a student at Miss Cackle’s Academy for Witches, who has two well-meaning friends and one nasty, aristocratic rival. Tamora Pierce wrote her “Circle of Magic” quartet, which also first published in 1997, about four budding mages who find themselves at Winding Circle, a temple community, and study magic from expert dedicates who live there. Set against this backdrop, Hogwarts seems like just another note in a familiar tune.

No one is totally original. Everyone builds on everyone else’s stories.Peter Glassman, founder of Books of Wonder

In an email interview with news, Pierce noted that the wizarding school was just one of many tropes revisited by “Harry Potter.” “The field at the time,” she wrote, “already had kids struggling through tough lessons and unfair teachers; something weird going on at school; hateful step-parents; boy heroes marked for Destiny with kill-crazy enemies; boy heroes with a swell flubsy boy pal and a super-smart girl pal; boy heroes with kindly mentors; boy heroes with pets; boy hero surprisingly good at sports; boy heroes with super powers/magic/weapons; seemingly unkillable Big Bads with zillions of evil minions.”

Not that this should be the point. Rowling may have been the first fantasy author some kids read, or Hogwarts the first magical school some fell in love with ― but even if she wasn’t actually the first, so what? “No one is totally original,” said Glassman. “Everyone builds on everyone else’s stories. So originality isn’t the thing.”

Besides, Pierce added, the world of Hogwarts did offer new delights. “Hidden school tunnels and rooms in which kids get into real trouble (Hogwarts is the most unsafe school ever!); a teacher who physically tortures the boy hero; consistent law-breaking and ‘justice served’ which corrects nothing at all,” she listed ― those, along with the sport of Quidditch, brought forward new, or at least newly popular, themes in children’s literature.

In our overwhelming eagerness to fête J.K. Rowling, though, it’s worth taking time to explore the full universe of children’s fantasy and to appreciate not only her forebears but her contemporaries and those who followed in her footsteps. “I think sometimes what gets lost in the noise is the accomplishment of all those other writers,” Glassman said. “Yes, what [Rowling] did was phenomenal. But a lot of other writers are doing wonderful things ― and I sometimes feel like, hey, what about them? And the people who came before?”

Once Rowling ― whom Glassman said he’s heard described as “a publisher’s dream”; good-looking, adept at being interviewed in any format, and a gifted author ― swept onto the scene, it was quickly impossible for any other author to keep pace with her fame, influence and acclaim. Children’s book writers, especially fantasy authors, who were once the masters of their domain found themselves ignored in media coverage and discussions of ”Harry Potter.”

Pierce, who had been writing fantasy for teenagers for years by then, said she always made it “a point of pride never to be jealous of another author.” Still, she found that “the bare mention of Harry or his writer made me surly.” For writers who had been creating inventive, compelling fantasy works for young readers for years, it must have been at least a bit infuriating to see a new author sweep in and garner all the credit for introducing kids to the magic of reading, and reading about magic. Then, Pierce said, she, along with other with YA writers and experts, participated in a panel exclusively devoted to the popularity of the three then-published ”Harry Potter” books. What was the secret sauce?

“By the time the panel was over, I was free,” she recalled. “Nobody knew. No one there could point to a single factor that made the books popular.”

All of the elements that kids seemed to latch onto in the series had been done before, they concluded. Rowling hadn’t discovered some new formula or concept that had captured a starved population of readers ― she’d used known elements of children’s literature to write the right books at the right time for the right readers.

That doesn’t mean Rowling wasn’t exceptionally creative, from her absurdly delightful wizarding vocabulary to the complex seven-book-long mystery arc she crafted. In fact, her most massive creation might have been the current middle-grade and young adult fiction market. If we think of popular pre-Rowling authors as big fish in a small pond, they may now look like smaller fish in comparison ― but the pond has become a Great Lake.

Harry Potter made the careers of many authors possible.Joe Monti, Editorial Director of Saga Press

The “Potter” craze, said Monti, “grew the market exponentially.” And when market demand grows, there are more opportunities for the people making the product ― in this case, that would be middle-grade and YA authors. ”Harry Potter,” he said, “made the careers of many authors possible.” With kids (and, yes, adults) clamoring for something to read in the long months and years between Rowling releases, publishers had a legitimate demand to meet: Fantasy sagas geared toward younger readers, and ultimately any sort of fiction written for middle-grade and young adult readers.

“When ‘HP’ first hit [the U.S.] in ’98, it certainly made an impact,” said Glassman. In his iconic children’s store, Books of Wonder, he noticed that “people were looking for books like that, because there was nothing else … we were selling a lot of Lloyd Alexander, E. Nesbit, obviously the “Narnia” books, The Hobbit, L.M. Boston.” Meanwhile, the publishing industry’s gears were turning. It takes a couple of years, Glassman pointed out, to jump on a new, unexpected publishing trend. Editors and agents have to find people writing similar books, acquire them, edit them and publish them, none of which can be accomplished overnight.

Eventually, though, it wasn’t just classics that were benefiting from the “Potter” mania. New authors were getting opportunities, too. Over the ensuing years, the sheer amount of books published for kids seems to have ballooned; in 2011, The Atlantic reported that the number of YA books had increased by a factor of 10 between 1997 and 2009. Those precise numbers have been disputed, but it’s not the only statistic. Year after year, annual sales statistics show that rising demand for children’s books is bolstering the entire publishing industry.

Though realist writers like John Green have also flourished in ”Harry Potter’s” wake, the effect seems to have been particularly powerful for genre writers. Gail Carson Levine, the Newbery Award–winning author of middle-grade fantasy tales, recalled that when she began paying close attention to the market in the 1990s, most books for younger readers were general fiction. After ”Harry Potter,” which debuted in the U.K. the same year that Carson Levine published her beloved fairy tale novel Ella Enchanted, she noticed that “there came to be more fantasy. It was very good for fantasy because it was a market that people knew existed.”

You can draw a dotted line to the mainstreaming of geek culture through ‘Harry Potter.’Joe Monti

Glassman noted that some of the books that followed in Harry’s footsteps may have been purely imitative, but the enduring demand the series had uncovered for fantasy in young readers allowed creativity in the genre to flourish. Books came out by fantasy authors who were encouraged by the Potter success, authors who might have thought to themselves, “I always wanted to write like that but didn’t think I could sell them,” he said.

It’s easy to forget, Monti explained, “really how disparaged fantasy was, as a genre, in children’s and YA literature — a bias that crossed into adult as well. The fact that ‘Harry Potter’ midnight release parties were the event to go to as a teen was completely unprecedented in geek culture. You can draw a dotted line to the mainstreaming of geek culture through ‘Harry Potter.’”

Pierce, who was already publishing high fantasy chronicles for teenagers when the ”Potter” craze struck, applauded this change. “Speaking as someone who was trashed to the dogs and back for reading ‘that junk’ and writing it,” she said, “I am pleased about this.”

Actually, ”Harry Potter” combined several qualities that publishers previously thought didn’t appeal much to kids: The somewhat nerdy genre of fantasy, extremely thick books, and a long series with an overarching narrative arc that demanded you start at the beginning and read the whole way through. All of these things may have existed in middle-grade and YA markets before “Potter,” but the conventional wisdom was that they were liabilities or ill-suited for the age group.

Carson Levine was, she says now, “astonished” at “how long [′Harry Potter’] was and how willing kids were to read that length. When I started, I was told at children’s book conferences that you had to stay under 200 pages.” Though she admits she didn’t stay under that target, the industry expectation was clear.

Pierce reiterated that the “most major” impact of ”Harry Potter” success was that it convinced people that kids would read longer books. “I would have thought that the popularity of Brian Jacques’ ′Redwall’ books, beginning in the mid-1980s, would have convinced publishers kids wanted longer books, but it took ′Harry Potter,’” she said.

Middle-grade and YA were once dominated by one-off books and by episodic series that seemed to have no beginning or end ― “Nancy Drew,” “Sweet Valley High,” “Baby-Sitters Club.” With the demand for Potter-esque franchises, Carson Levine pointed out, came an embrace of a different sort of YA brand. No longer did publishers assume that kids didn’t have the patience or attention span for a single quest split across two or more books. Grandiose sagas for kids with “that very big story arc,” Carson Levine said ― “Hunger Games,” “Twilight,” “Divergent,” “The Red Queen” ― became popular.

“Harry Potter” also did something both necessary, because of its length and massive fanbase, and risky, because it makes it difficult for new readers to binge-read the whole series. It began as a middle-grade series, then grew steadily darker, longer and more challenging. By the time Deathly Hallows, the final book in the series, published, the series had clearly leveled up to young adults. The themes of budding sexuality, battlefields strewn with fatalities and ultimate self-sacrifice seem geared more toward teenagers than toward 10-year-olds. Of course, the series’ initial fans got to grow up with the books and see out the mystery that had hooked them from the beginning. But it’s a tricky model for children’s literature; whereas you can read as many “Baby-Sitters Club” books as you like for as long as you are in the target age range and then stop, a saga like ”Harry Potter” that evolves to span multiple age ranges makes it more challenging for anyone to read the entire series within one year.

Despite the challenges posed by Harry’s, and the “Harry Potter” books’, coming of age, Jonathan Alexander, Chancellor’s Professor of English at the University of California, Irvine, sees it as one of the series’ most powerful draws. “You don’t get a lot of those series such that the readers are growing up with the characters,” he pointed out. There is precedent, of course; he cited Anne of Green Gables, which was published over 100 years ago, and follows a spunky orphan from childhood into adulthood. Stories about young people who come of age over the course of the work have often, historically, been popular ― they’ve just been marketed toward adults. Even the serialized nature of the bildungsroman arc isn’t new. “It’s not at all dissimilar from David Copperfield, in which Dickens lays out […] the story of David Copperfield that you could follow over time, and watch him develop to adulthood,” he said. “That was pitched primarily to adults.”

Alexander argued that there’s a universal fascination with growing up, even though books specifically about young people are typically viewed as best suited for kids. “I think we’re fascinated by the development process,” he said. “It’s not just for young readers to have a model, but for older readers themselves to meditate on how we grow up.” No wonder, then, that the ”Potter” books found an eager adult audience. As the series evolved, it became more and more similar to books that have, in the past, been marketed to grown-ups: stories of young people learning to make their way in a frightening and unpredictable world. The post-”Potter” Y.A. world, Alexander suggested, has skewed more toward the sort of sophisticated, complex coming-of-age novels that have always appealed to adults ― and adults and young adults alike are devouring them.

A healthy portion of the new popularity of young adult fiction can be attributed to these enthusiastic adult readers, but it seems that the ”Harry Potter” phenomenon has also reinvigorated reading among young people. In 2011, McSweeney’s noted that according to the NEA, between 1982 and 2002, the number of young adults who read literature had dropped by 20 percent. In 2009, the NEA found that this stat had rebounded ― between 2002 and 2008, young adult readership had risen 21 percent.

Numbers can be tricky, though. We simply don’t know for sure how much of this increase can be directly traced to “Harry Potter.” Much like Harry himself ― an exceptional hero whose victory over dark magic likely depended on a host of less-famous heroes, from Hermione and Ron to Neville Longbottom and Mrs. Weasley ― the books are often singled out as the sole savior of YA, but it’s unlikely they alone built the bountiful children’s literary landscape we have today. Perhaps the children’s book world was waiting for a savior, and Rowling just happened to arrive with the sword of Gryffindor. Perhaps the “Potter” phenomenon merely accelerated an inevitable growth in the sector.

“Speaking as someone who was trashed to the dogs and back for reading ‘that junk’ and writing [fantasy], I am pleased about this.”Tamora Pierce

With a healthy and thriving middle-grade and YA market, chances are we’ll never again see something like “Harry Potter”: A children’s book saga that captures the imagination of the entire world and leaves us forever changed. Inside the YA world, authors and professionals who spoke to news said people aren’t expecting to find another “Harry Potter.” Superstars, pointed out Glassman, come from specific circumstances. “Babe Ruth was just the right time to be the legend he was,” he explained — and so was Rowling. “There’s never going to be another J.K. Rowling,” Glassman said.

Instead, today’s YA authors are playing inside a much larger sandbox, working for a known audience and pushing boundaries in other ways. “We’re finally publishing more fantasy — and especially science fiction —from voices that have been marginalized in the past,” said Monti. In Rowling’s books, and in many past fantasy hits, the main characters were white, straight, cisgender and able-bodied. Though the literary world remains far too white, authors like Sabaa Tahir (An Ember in the Ashes), Ellen Oh (Prophecy), and general fiction writer Angie Thomas (The Hate U Give) have begun to make inroads with more diverse protagonists. ”This pattern needs to keep growing,” Monti said, “because the idea that LGBTQ and brown kids don’t read or sell is a rear window view.”

“Harry Potter” blew the roof off of children’s literature. But that doesn’t mean the work is done — for YA authors, it just means more scope for the imagination.

From June 1 to 30, news is celebrating the 20th anniversary of the very first “Harry Potter” book by reminiscing about all things Hogwarts. Accio childhood memories.